Cables used, for example, the wiring of a computer are very easily affected by external interference, and the cable is generally shielded. This type of shielded cable, for example, as shown in FIG. 4, comprises a drain conductor 4 arranged at the side of an insulated conductor 3, which includes a signal conductor 1 covered by an insulation sheath 2. The drain conductor is covered with a shield 5 of an aluminum foil, and a plurality of the shielded conductors are arranged in parallel and then integrally covered with an outer insulation jacket 6. The drain conductors 4 are connected with a ground terminal, and therefore, the shield 5 is also connected to ground to protect the signal conductors 1 connected to signal terminals from external interference.
However, in this type of shielded cable, as the shield is made of an aluminum foil, the direct current resistance is comparatively large, and further, the flexibility is unsatisfactory. Accordingly, a shielded cable using a shield of copper wires instead of aluminum foil is being used. As shown in FIG. 5, the shielded cable 10 comprises a plurality of fine copper shielding wires 7 spirally wound around the insulated conductor 3 comprising a signal conductor 1 covered with an inner insulation sheath 2, and a plurality of the shielded conductors 3 wound with the shielding wires 7 defining shielded conductors are arranged laterally in parallel. A drain conductor 4 is arranged at the side of each shielded conductor 3 in electrical engagement with the shielding wires 7 thereof; conductors 3, shielding wires 7 and drain conductors 4 are then integrally covered with an outer insulation jacket 6. The direct current resistance of shielded cable 10 is small, interference is efficiently prevented, and further, the handling of the cable is made easier because of enhanced flexibility.
When using the shielded cable 10 shielded with the spiral wound shielding wires 7, as shown in FIG. 5, an electrical connector is connected with prepared end portions of the cable, and thus a connection between the cable 10 and a mating electrical connector can be readily effected. The following is an explanation of the method of connecting the end portions of the cable 10 with the connector.
FIGS. 6A to 6E successively show the process whereby the signal conductors 1 and drain conductors 4 are exposed at the end portion of the shielded cable 10 and connected with specified terminals of electrical connector 8. First, as shown in FIG. 6A, only the outer insulation jacket 6 is cut at a right angle to the cable axis at a distance d1 from one end 10a toward the center portion of the shielded cable 10. Namely, only the outer insulation jacket 6 is cut along the dotted line in FIG. 6A. Next, the cut end portion 10a of the outer insulation jacket 6 is removed from the cable, and the spiral wound shielding wires 7 are then unwound and separated into upper and lower rows to allow the insulated conductors 3 and the drain conductors to be exposed as shown in FIG. 6B. Then the shielding wires 7, which have been separated into upper and lower rows, are cut and the remaining ends of wires 7 are bent backwardly over insulation jacket 6 and further, the inner insulation portions 2 are removed to allow the signal conductors 1 to be exposed, as shown in FIG. 6D. Next, each signal conductor 1 is connected with each specified electrical terminal of connector 8, and the drain conductors are also connected with ground terminals of connector 8.
Although the end portion of the shielded cable 10 is connected with the connector 8, the following problems are apt to arise. First, when the spiral wound shielding wires 7 are being unwound as shown in FIG. 6B, there is a possibility that the spacing of each of the conductors 3 and 4 may be changed by fraying of the insulated conductors 3 and the drain conductors 4, and by the conductors 3 and 4 being bent. If the spacing of each of the conductors 3 and 4 is changed, it will not correspond with the spacing of each terminal of the connector 8, and therefore, a problem arises in that it becomes difficult to connect them with each terminal of the connector 8 shown in FIG. 6E. Second, since the spacing of the insulated conductors 3 is small, and the insulated conductors are arranged close together, the spiral wound shielding wires 7 cannot be completely unwound, thus, there is also a possibility that some of the shielding wires 7 may remain between the insulated conductors 3. If some of the shielding wires 7 remain in this position, these remaining shielding wires 7 can contact with the signal conductors 1, which are connected with each terminal of the connector 8, therefore a problem arises in that the signal conductors are connected to ground. Third, although the unwound shielding wires 7 are bent back as shown in FIG. 6C, the shielding wires 7 may spring or move back and make contact with signal conductors 1, therefore, the signal conductors are connected to ground.